An introduction of particles into the vasculature of a patient requires simultaneously satisfying several different concerns or considerations. Depending on the type of particles involved, a concern of significant importance involves preventing the particles from flocculating, i.e. clumping together, as they are being infused or introduced into the vasculature. This is of particular concern in the case of stem cells which can flocculate, but which are most effective in therapy if left to function either as individual cells or in small groups of cells. An additional benefit of preventing particles from flocculating is the prevention of heart attacks caused when clumps of cells are introduced into the coronary circulatory system. Also, it is possible that the retention rate of stem cells in the heart, or other targeted tissue, will increase when the stem cells are infused while flow is slow when the valve or the balloon might help in reducing blood flow.
In all types of intravascular therapy (i.e. intracoronary, intra-arterial or intravenous), it is always an essential concern that the therapeutic agent (e.g. biologics or drugs) be infused or delivered in a predictably controlled manner. Furthermore, it is important that the therapeutic agent be effectively delivered to a proper destination in the vasculature. All of this involves dosage and delivery rate considerations. Moreover, it requires careful handling of the therapeutic agent to insure it (the therapeutic agent) is not damaged or otherwise compromised during an infusion.
From a mechanical perspective, it is known that the diameter of a fluid passageway is a factor that will affect the rate of fluid flow through the passageway. For protocols where small groups of de-flocculated particles are to be infused into a vessel of a vasculature, the diameter of the passageway must obviously be large enough to individually accommodate the small groups of particles. On the other hand, it must also be small enough to separate and prevent larger groups of particles (cells) from clinging to each other. A consequence of this is that the rate at which particles can be carried through the passageway will be circumscribed by the dimensions of the passageway. A further consequence of this is that, as particles leave the passageway, they are then influenced by the flow of fluid (i.e. blood) in the vessel of the vasculature. Depending on the purpose of the protocol, this may mean that the downstream fluid flow in the vasculature will somehow also need to be regulated.
In some cases, the downstream fluid flow in the vasculature (discussed above) can be controlled or regulated using an inflatable balloon that is attached to an outside surface of the catheter tube. For these and similar arrangements, when the balloon is deployed at the treatment site (i.e. inflated), a pressure is exerted on the catheter tube. The catheter tube, however, is typically made of a flexible material to allow it to twist and turn as the catheter is navigated through the patient's vasculature. Because of the flexible nature of the catheter tube, it is typically susceptible to kinking and/or collapse during inflation of the balloon. This can be particularly troublesome for infusion catheters where the material to be infused is pumped through a central lumen of the catheter tube. In this instance, a collapse or even partial blocking of the central lumen where the balloon is inflated can impede fluid flow in the central lumen, and adversely affect an infusion procedure. In addition to reducing flow, a collapsed or blocked catheter tube lumen can reduce cell viability during transport through the lumen by exposing the cells to stress (Note: in some cases, viability has been found to be lowered by around 70-80% when flow is impeded in the central lumen).
In light of the above, it is an object of the present invention to provide an infusion system that can effectively introduce only small groups of particles into a fluid flow. Another object of the present invention is to provide an infusion system that coordinates the flow rate of a particle/fluid medium (i.e. a first fluid) with the flow rate of a fluid (i.e. a second fluid) into which the particle/fluid medium is being introduced. Still another object of the present invention is to provide an infusion system that produces a low exit pressure to reduce the impact on a vessel wall caused when fluid exits a catheter and enters the vessel. It is still another object of the present invention to provide an infusion system having a balloon to regulate blood flow at an infusion site that is not subject to central lumen collapse or blocking during balloon inflation. Yet another object of the present invention is to provide an infusion system that is easy to use, is simple to manufacture and is comparatively cost effective.